Hi Mike,
The Opies were as you describe, experienced, but they were prone to occasional lapses.
This from Lore and Language of Schoolchildren, pps 95-96
Jim Carroll

"Genuinely erotic verse, however, is unusual. That there are villains among children, as among adults, the News of the World offers frequent testimony; and from somewhere the ogre child acquires his strange salacious prescriptions, taking criminal pleasure in pressing them on
juniors, and inscribing them on the walls of the school lavatory. But we are not here discussing delinquents. The usual group of youngsters whispering together, passing some verse to each other and giggling, though they refuse to tell what it is, are probably interested in nothing more sordid than the deeds of nature, an intimate garment, or a crude word."